C 语言学习笔记：浮点数类型详解

浮点数

代码

void day2() {
    // 定义一个浮点数 π
    float pi = 3.141592653589793238462643383279502884197169399375105820974944592307816406286f;
    // 定义一个双精度浮点数 π
    double pi2 = 3.141592653589793238462643383279502884197169399375105820974944592307816406286;
    // 定义一个长双精度浮点数 π
    long double pi3 = 3.141592653589793238462643383279502884197169399375105820974944592307816406286l;

    // 打印浮点数
    cout << pi << endl;
    // 打印双精度浮点数
    cout << pi2 << endl;
    // 打印长双精度浮点数
    cout << pi3 << endl;

    // setprecision() 设置精度
    cout << setprecision(100) << pi << endl;
    cout << setprecision(100) << pi2 << endl;
    cout << setprecision(100) << pi3 << endl;

    // 完整的打印出来
    cout.precision(100);
    cout << pi << endl;
    cout << pi2 << endl;
    cout << pi3 << endl;

    // 打印结果如下
    // 3.14159
    // 3.14159
    // 3.14159
    // 3.1415927410125732421875
    // 3.141592653589793115997963468544185161590576171875
    // 3.141592653589793115997963468544185161590576171875
    // 3.1415927410125732421875
    // 3.141592653589793115997963468544185161590576171875
    // 3.141592653589793115997963468544185161590576171875
}

每种数据占用的字节数 范围

// 每种数据占用的字节数 范围
void dataType() {
    // char 1 字节 -128 ~ 127
    // unsigned char 1 字节 0 ~ 255
    // short 2 字节 -32768 ~ 32767
    // unsigned short 2 字节 0 ~ 65535
    // int 4 字节 -2147483648 ~ 2147483647
    // unsigned int 4 字节 0 ~ 4294967295
    // long 4 字节 -2147483648 ~ 2147483647
    // unsigned long 4 字节 0 ~ 4294967295
    // long long 8 字节 -9223372036854775808 ~ 9223372036854775807
    // unsigned long long 8 字节 0 ~ 18446744073709551615
    // float 4 字节 3.4E-38 ~ 3.4E+38
    // double 8 字节 1.7E-308 ~ 1.7E+308
    // long double 16 字节 3.4E-4932 ~ 1.1E+4932

    cout << "type: \t\t" << "************size**************"<< endl;
    cout << "bool: \t\t" << "所占字节数：" << sizeof(bool);
    cout << "\t最大值：" << (numeric_limits<bool>::max)();
    cout << "\t\t最小值：" << (numeric_limits<bool>::min)() << endl;
    cout << "char: \t\t" << "所占字节数：" << sizeof(char);
    cout << "\t最大值：" << (numeric_limits<char>::max)();
    cout << "\t\t最小值：" << (numeric_limits<char>::min)() << endl;
    cout << "signed char: \t" << "所占字节数：" << sizeof(signed char);
    cout << "\t最大值：" << (numeric_limits<signed char>::max)();
    cout << "\t\t最小值：" << (numeric_limits<signed char>::min)() << endl;
    cout << "unsigned char: \t" << "所占字节数：" << sizeof(unsigned char);
    cout << "\t最大值：" << (numeric_limits<unsigned char>::max)();
    cout << "\t\t最小值：" << (numeric_limits<unsigned char>::min)() << endl;
    cout << "wchar_t: \t" << "所占字节数：" << sizeof(wchar_t);
    cout << "\t最大值：" << (numeric_limits<wchar_t>::max)();
    cout << "\t\t最小值：" << (numeric_limits<wchar_t>::min)() << endl;
    cout << "short: \t\t" << "所占字节数：" << sizeof(short);
    cout << "\t最大值：" << (numeric_limits<short>::max)();
    cout << "\t\t最小值：" << (numeric_limits<short>::min)() << endl;
    cout << "int: \t\t" << "所占字节数：" << sizeof(int);
    cout << "\t最大值：" << (numeric_limits<int>::max)();
    cout << "\t最小值：" << (numeric_limits<int>::min)() << endl;
    cout << "unsigned: \t" << "所占字节数：" << sizeof(unsigned);
    cout << "\t最大值：" << (numeric_limits<unsigned>::max)();
    cout << "\t最小值：" << (numeric_limits<unsigned>::min)() << endl;
    cout << "long: \t\t" << "所占字节数：" << sizeof(long);
    cout << "\t最大值：" << (numeric_limits<long>::max)();
    cout << "\t最小值：" << (numeric_limits<long>::min)() << endl;
    cout << "unsigned long: \t" << "所占字节数：" << sizeof(unsigned long);
    cout << "\t最大值：" << (numeric_limits<unsigned long>::max)();
    cout << "\t最小值：" << (numeric_limits<unsigned long>::min)() << endl;
    cout << "double: \t" << "所占字节数：" << sizeof(double);
    cout << "\t最大值：" << (numeric_limits<double>::max)();
    cout << "\t最小值：" << (numeric_limits<double>::min)() << endl;
    cout << "long double: \t" << "所占字节数：" << sizeof(long double);
    cout << "\t最大值：" << (numeric_limits<long double>::max)();
    cout << "\t最小值：" << (numeric_limits<long double>::min)() << endl;
    cout << "float: \t\t" << "所占字节数：" << sizeof(float);
    cout << "\t最大值：" << (numeric_limits<float>::max)();
    cout << "\t最小值：" << (numeric_limits<float>::min)() << endl;
    cout << "size_t: \t" << "所占字节数：" << sizeof(size_t);
    cout << "\t最大值：" << (numeric_limits<size_t>::max)();
    cout << "\t最小值：" << (numeric_limits<size_t>::min)() << endl;
    cout << "string: \t" << "所占字节数：" << sizeof(string) << endl;
    // << "\t最大值：" << (numeric_limits<string>::max)() << "\t最小值：" << (numeric_limits<string>::min)() << endl;
    cout << "type: \t\t" << "************size**************"<< endl;
}